Stabilized saturated cyclic ether compositions



United States Patent 3,029,257 STABILIZED SATURATED CYCLlC ETHERCOMPOSITIONS Hugh C. Campbell, Wilmington, Del., assignor to E. I.

du Pont de Nemours and Company, Wilmington, Del.,

a corporation of Delaware No Drawing. Filed Nov. 20, 1959, Ser. No.854,236

2 Claims. (Cl. 260-3461) This invention relates to the stabilization ofcyclic ethers, particularly saturated ethers and more particularly tothe stabilization of tetrahydrofuran.

Tetrahydrofuran and related compounds are susceptible to oxidation andhave a tendency to form peroxides Peroxides are especially undesirablebecause if permitted to increase to high concentrations, the materialcan become too unsafe for handling. Peroxides usually form under storageconditions when the ether is in contact with air. Additional peroxideformation can occur when the ether is used and exposed to light and air.In order to prevent the peroxide from exceeding safe limits, it isnecessary to employ stabilizers or antioxidants that either destroy theperoxide, inhibit its formation, or both.

A preferred stabilizer in addition to effectively suppressing peroxideformation or accumulation is one that is non-toxic and substantiallycolorless. Additionally, the stabilizer should be effective when used atlow concentrations. Known antioxidants are frequently unsuitable eitherbecause they do not suppress peroxide formation or accumulation to asufficiently low level or because they do not possess the abovecharacteristics.

It has been found that excellent stabilization can be obtained using4,4-thiobis-(6-tertiary-butyl-m-cresol). The above-disclosed stabilizeris essentially nontoxic and tetrahydrofuran and related compoundsstabilized according to the present invention remain substantiallycolorless under the influence of air and light.

It is an object of the present invention to provide a stabilized cyclicether composition that does not develop excessive peroxide formation.

It is another object of the present invention to provide a stabletetrahydrofuran composition that does not become discolored under theinfluence of light and air.

It is still another object to provide a method of effectivelystabilizing tetrahydrofuran and related ethers against peroxideformation.

These and other objects will be apparent from the following examples anddescription.

Concentrations of less than 0.01 to more than 1% by weight of4,4-thiobis-(6-tertiary-butyl-m-cresol) are effective in preventingperoxide formation in saturated cy- ICC clic ethers and relatedcompounds. More than 1% by weight can be used but preferredconcentrations are those having 0.01 to 0.1% by weight of thestabilizer.

Two 250 ml. Erlenmeyer flasks were equipped with cork stoppers fittedwith tubing which permitted the entrance of air. A ml. sample oftetrahydrofuran was placed in each flask and about 0.1 gm. of4,4'-thiobis- (6-tertiary-butyl-m-cresol) was introduced into onesample. The tetrahydrofuran used had a very low peroxide content whenreceived (less than 50 ppm). The flask was constantly exposed to lightand air for an extended period of time at room temperature andtetrahydrofuran peroxide content (ppm) was determined periodically asfollows:

Tetrahydrofuran Peroxide (p.p.n1.) Days of Exposure From the above itcan be seen that the 4,4-thiobis-(6- tertiary-butyl-m-cresol) stabilizerhad an extraordinary effect in preventing peroxide formation. Inaddition to containing a non-toxic stabilizer, the stabilizedcomposition remained colorless throughout the experiment.

Other cyclic ethers which can be stabilized in accordance with thepresent invention include methyl tetrahydrofuran and tetrahydropyran.

The embodiments of the invention in which an exclusive property orprivilege is claimed are defined as follows:

1. A stabilized composition consisting essentially of a saturated cyclicether selected from the group consisting of tetrahydrofuran, methyltetrahydrofuran, and tetrahydropyran and from 0.01 to 1% by weight4,4'-thiobis- (o-tertiary-butyl-m-cresol) 2. A stabilized compositionconsisting essentially of tetrahydrofuran and about 0.01 to 0.1% byweight 4,4- thiobis- 6-tertiary-butyl-m-cresol References Cited in thefile of this patent Thompson et al.: Ind. and Eng. Chem, vol. 42, pages922-925 (1950).

Katsui et al.: Chem. Abstracts, vol. 51 (1957), columns 15, 887-8.

1. A STABILIZED COMPOSITION CONSISTING ESSENTIALLY OF A SATURATED CYCLICETHER SELECTED FROM THE GROUP CONSISTING OF TETRAHYDROFURAN, METHYLTETRAHYDROFURAN, AND TETRAHYDROPYRAN AND FROM 0.01 TO 1% BY WEIGHT4,4''-THIOBIS(6-TERTIARY-BUTYL-M-CRESOL)